It was a large but elegant mechanism, built of polished walnut and oak, of brass and glass, copper and mirrors and carved and inlaid ivory, of quartz prisms and brass gears and springs and cogs. The whole thing was rather larger than a wide-screen television, although the actual screen itself was no more than six inches across. A magnifying lens placed across it increased the size of the picture. There was a large brass horn coming out of the side—the kind you could find on an antique gramophone. The whole mechanism looked rather like a combined television and video player might look, if it had been invented and built three hundred years ago by Sir Isaac Newton. Which was, more or less, exactly what it was.